I would ask the internist for a referral to a neurologist and an ENT doc. All you describe just doesn't sound like it's all anxiety. Are you taking the pill to lower your heart rate only when it's fast? I'm wondering if it could make your pulse too slow at normal times thus causing some of your symptoms. Can you take your pulse when you feel bad and keep a record? If your doc doesn't take you seriously, time for another viewpoint.